JP5859131B2 - Antifouling coating, heat exchanger provided with the same, and manufacturing method thereof - Google Patents

Description

  The present invention relates to an antifouling coating capable of suppressing adhesion of dirt to a surface and a heat exchanger provided with the same. In particular, the present invention relates to antifouling coatings and heat exchangers for air conditioners used in metal processing sites such as welding and cutting, establishments handling metal dust, vehicles such as railways, and related facilities.

Various product surfaces are exposed to various pollutants from the environment, so that they look dirty, cause sanitary problems, and cause deterioration in performance due to corrosion or the like. Among them, the heat exchanger in the air conditioner is very susceptible to environmental pollution due to its function, and various inconveniences are easily caused by the contamination.
The heat exchanger has a structure in which a large number of fins (for example, aluminum fins) are attached to a pipe through which a refrigerant passes, and heat exchange efficiency is enhanced by fins having a large surface area. Condensed water tends to adhere to the surface of the fins during cooling and heating, and the resistance to heat exchange is reduced due to the phenomenon that the fins are blocked by condensed water (hereinafter referred to as “bridge phenomenon”). There is. In particular, the bridging phenomenon is likely to occur when dirt such as dust adheres to the fin surface, so the bridging phenomenon is achieved by forming an organic or inorganic hydrophilic coating with excellent antifouling performance on the fin surface. Is generally prevented. Here, “antifouling performance” in the present specification means a performance in which dirt is difficult to adhere and a performance in which attached dirt is easily removed.

However, when the inorganic hydrophilic coating contains a large amount of inorganic components such as water glass and boehmite, odor adsorption is likely to occur. Therefore, an organic hydrophilic coating is often used. On the other hand, organic hydrophilic coatings are likely to decompose or deteriorate organic components or dissolve in condensed water with the passage of time, so that the antifouling performance and hydrophilicity of the hydrophilic coating are lowered.
Therefore, in order to prevent the antifouling performance and hydrophilicity of such a hydrophilic coating from being reduced, techniques for forming the hydrophilic coating using various paints have been proposed. For example, Patent Document 1 proposes a method of forming a hydrophilic coating using a paint containing modified polyvinyl alcohol and a crosslinking agent. Patent Document 2 proposes a method of forming a hydrophilic coating using a paint containing carboxymethylcellulose, polyethylene glycol, and a crosslinking agent. Patent Document 3 proposes a technique for forming a thin film made of silica ultrafine particles and fluororesin particles. By adopting a configuration in which hydrophobic portions are scattered on the hydrophilic surface, it is possible to suppress the adhesion of dirt having various hydrophilic or hydrophobic properties while maintaining high hydrophilicity as a whole film. Since it is a thin film, problems such as odors can be avoided, and adaptation to a heat exchanger is also possible.

JP 10-36757 A JP-A-8-261688 International Publication No. 2008/087877

  In general, antifouling coatings are exposed to water, heat, light, air, etc., so that their antifouling performance and hydrophilicity are reduced, or metal such as the underlying fins and resin are deteriorated due to coating deterioration. May happen. Also, especially when there are many metal particles of iron, copper or their alloys as contaminants, especially iron powder, it tends to cause the antifouling performance and hydrophilicity of the hydrophilic coating and cause corrosion of the fins. . Patent Documents 1, 2, and 3 do not deal with the problems regarding the antifouling performance and hydrophilicity degradation of the hydrophilic coating due to the adhesion of the contaminants and the corrosion of the fins.

  That is, the hydrophilic coatings of Patent Documents 1, 2, and 3 can maintain antifouling performance and hydrophilicity in a normal environment where there are few contaminants such as metal particles in the air, but metal particles, etc. In environments where there are many pollutants (for example, metal processing sites such as welding and cutting, establishments handling metal dust, vehicles such as railways, and other related facilities), antifouling performance and hydrophilicity due to adhesion of contaminants Sexually decreases. Specifically, since the hydrophilic coatings of Patent Documents 1 and 2 are organic, the metal ion component generated by the dissolution of the pollutant in the condensed water acts as a catalyst to promote the deterioration of the organic component. . As a result, the antifouling performance and hydrophilicity of the hydrophilic coating are reduced, and fin corrosion and the like also occur. Also in Patent Document 3, metal particles or the like slightly adhered corrode on the surface, so that metal ions permeating through the thin film deteriorate the base, or the surface of the silica ultrafine particles adheres to the corroded iron powder. As a result, antifouling performance and hydrophilic deterioration may be caused.

  The present invention has been made to solve the above-described problems, and can maintain antifouling performance and hydrophilicity even in an environment where there are many contaminants such as metal particles in the air, and can prevent corrosion of fins. An object of the present invention is to provide an antifouling coating that can be prevented, a heat exchanger provided with the same, and a method for producing the same.

  As a result of diligent research to solve the above problems, the inventors of the present invention have a specific proportion of silica ultrafine particles having a specific average particle diameter and at least one zirconium compound selected from zirconium chloride and zirconyl chloride. And found that the antifouling coating formed from the aqueous coating composition contained in can maintain antifouling performance and hydrophilicity even in an environment where there are many contaminants such as metal particles in the air. It came to do.

That is, the present invention comprises 0.1 to 10 wt% of the ultrafine silica particles having an average particle size of 2 5 nm or less, 5 at least one zirconium compound selected from zirconium chloride and zirconyl chloride of the ultrafine silica particles 50% by mass of fluororesin particles having an average particle diameter of 50 to 500 nm are contained in an amount of 70:30 to 95: 5 in a mass ratio of the silica ultrafine particles to the fluororesin particles, and water is contained in 30 to 30 %. The antifouling coating is formed from an aqueous coating composition containing 99.5% by mass.

The present invention is also a heat exchanger comprising a pipe through which a refrigerant passes and a fin attached to the pipe, the hydrophilic organic coating formed on the fin, and a surface layer of the hydrophilic organic coating At least the one reaction layer and the zirconium compound is reacted in the aqueous coating to a reaction layer containing 0.1 to 10% by weight of ultrafine silica particles having an average particle size of 2 5 nm or less which is selected from zirconium chloride and zirconyl chloride A heat exchanger characterized by having an inorganic coating formed from the composition.

Furthermore, the present invention is a heat exchanger comprising a pipe through which a refrigerant passes and a fin attached to the pipe, the hydrophilic organic coating formed on the fin, and on the hydrophilic organic coating, It comprises 0.1 to 10 wt% of the ultrafine silica particles having an average particle size of 2 5 nm or less, at least one zirconium compound selected from zirconium chloride and zirconyl chloride containing 5 to 50 wt% of the ultrafine silica particles and water And an inorganic coating formed from a water-based coating composition containing 30 to 99.5% by mass of the heat exchanger.

  According to the present invention, it is possible to form an antifouling coating that has high hydrophilicity and antifouling properties and is less likely to cause adhesion and deterioration of dirt even in the presence of metal particles and the like. In addition, the heat exchanger provided with the fins on which the antifouling coating is formed can maintain the antifouling performance and hydrophilicity even in an environment where there are many contaminants such as metal particles in the air and the corrosion of the fins. Is prevented.

It is a schematic diagram explaining deterioration of the conventional coating by adhesion of a metal particle. It is a schematic diagram explaining that the antifouling coating which concerns on Embodiment 1 of this invention does not deteriorate easily by adhesion of a metal particle. It is a schematic diagram explaining deterioration of the conventional coating by adhesion of a metal particle. It is a schematic diagram explaining that the antifouling coating which concerns on Embodiment 2 of this invention does not deteriorate easily by adhesion of a metal particle.

Embodiment 1 FIG.
At metal processing sites such as welding and cutting, establishments handling metal dust, railway vehicles and related facilities, etc., metal particles such as iron, copper, zinc and their alloys, or particles attached to them float in the air. (Hereinafter, these are collectively referred to as metal particles). Coatings of inorganic substances, organic substances, or composites thereof, particularly highly hydrophilic coatings having a large number of polar groups such as hydroxyl groups on the surface, are easily deteriorated due to the adhesion of metal particles, and the metal particles are liable to adhere.
FIG. 1 is a schematic diagram for explaining deterioration of a conventional coating due to adhesion of metal particles. In FIG. 1, the conventional coating has silica ultrafine particles 11 as inorganic fine particles accumulated and dotted with fluororesin particles 12. As will be described later, the coating having such a structure hardly adheres to dust, but when wet with water, the metal particles 13 (for example, iron powder) adhere. Part of the metal particles 13 corrodes with moisture, so that metal ions 14 adsorbed on the silica ultrafine particles 11 in the coating are formed. In such a state, the metal particles 13 are firmly fixed to the coating, so that the coating is soiled and the antifouling property is deteriorated due to the fixed metal particles 13.

  On the other hand, the aqueous coating composition for obtaining the antifouling coating according to Embodiment 1 of the present invention contains silica ultrafine particles 11, at least one zirconium compound selected from zirconium chloride and zirconyl chloride, and water. It is. By applying this aqueous coating composition to the surface of the article and drying it, it is possible to exhibit high durability and antifouling property against the reaction caused by the reaction and corrosion caused by the metal ions 14, and the environment in which the metal particles 13 are likely to adhere. In addition, an antifouling coating exhibiting good hydrophilicity and antifouling property can be formed. FIG. 2 is a schematic diagram for explaining that the antifouling coating 15 according to Embodiment 1 is hardly deteriorated by the adhesion of the metal particles 13. In FIG. 2, Zr atoms 16 introduced by zirconium chloride or zirconyl chloride form a bond with a hydroxyl group or the like on the surface of the silica ultrafine particles 11 and have an effect of protecting the surface of the antifouling coating 15. The introduced Zr atom 16 acts as a protective group for the hydroxyl group present on the surface of the antifouling coating 15, so that adsorption of metal ions 14 such as iron ions generated from the metal particles 13 and adhesion of the metal particles 13 can be suppressed. It is done. In FIG. 2, the hydrophobic fluororesin particles 12 are scattered on the hydrophilic silica thin film. However, the fluororesin particles 12 further suppress the adhesion of dust, and even without this, The effect of suppressing the sticking of the metal particles 13 by adding zirconium chloride or zirconyl chloride can be obtained. That is, the surface of the antifouling coating 15 has a structure in which a hydrophilic portion is continuous although a hydrophobic portion is present, so that it easily spreads when a water droplet adheres, and has a high hydrophilicity when viewed as a whole film. Will have sex. In addition, since the hydrophilic portion and the hydrophobic portion are finely mixed together, it will be in contact with the surface of the opposite property regardless of whether hydrophilic dust or hydrophobic dust adheres. It cannot adhere and exhibits high antifouling properties against a wide range of dust contamination.

  There are various organometallic compounds that function similarly to zirconium chloride and zirconyl chloride, such as chelates or alkoxides other than chlorides, titanium and aluminum in addition to zirconium. However, compared with these compounds, zirconium chloride and zirconyl chloride can be stably present as a hydroxide of zirconium when added to an aqueous coating composition containing water as a main component (zirconium chloride is present in an aqueous solution). Furthermore, it becomes zirconyl chloride), and at the time of forming the coating, it exhibits high reactivity and can effectively suppress the influence of the metal particles 13. In addition, when at least one zirconium compound selected from zirconium chloride and zirconyl chloride is added to the aqueous coating composition, hydrochloric acid or the like is generated as a by-product, but hardly remains in the antifouling coating 15 and remains. However, the effect on antifouling properties is small. Zirconium chloride and zirconyl chloride are also advantageous in that they are highly safe for the human body. When other organometallic compounds are added, various by-products resulting from the chelate or alkoxide are produced, which may affect the antifouling performance and the like.

The content of at least one zirconium compound selected from zirconium chloride and zirconyl chloride is 5% by mass or more and 50% by mass or less, preferably 10% by mass or more and 40% by mass or less, based on the solid content weight of the ultrafine silica particles. It is. When the content of the zirconium compound is less than 5% by mass, the influence of the metal particles 13 cannot be sufficiently suppressed. On the other hand, when the content of the zirconium compound exceeds 50% by mass, the pores of the porous silica film formed by the aggregation of the silica ultrafine particles 11 are filled with the zirconium compound, so that the antifouling coating 15 becomes too dense, Since antifouling performance falls, it is not preferable. Here, the content of the zirconium compound is calculated based on the mass of zirconium oxide when all the zirconium in the added zirconium compound becomes zirconium oxide (ZrO ₂ ).

  As the silica ultrafine particles 11 in the present invention, colloidal silica and fumed silica can be used. The average particle diameter of the silica ultrafine particles 11 may be 25 nm or less, preferably 3 nm or more and 25 nm or less, more preferably 5 nm or more and 15 nm or less. Here, the “average particle diameter” of the silica ultrafine particles 11 in the present specification is based on the number of primary particles of the silica ultrafine particles 11 measured with a laser light scattering type or dynamic light scattering type particle size distribution meter. Mean value of average particle size. If the average particle size of the silica ultrafine particles 11 is too small, it may be difficult to uniformly disperse in the aqueous coating composition, and the dust adhesion suppressing effect by the antifouling coating 15 may be difficult to obtain. On the other hand, if the average particle diameter of the silica ultrafine particles 11 exceeds 25 nm, the strength of the antifouling coating 15 is weakened, and practical durability may not be obtained. Here, the dust adhesion suppressing effect of the antifouling coating 15 is obtained because the antifouling coating 15 is a porous silica film formed by aggregation of the silica ultrafine particles 11. Since the antifouling coating 15 is a porous silica film, the contact area becomes very small even if dust collides, and the intermolecular force acting between the dust and the film is also small because the density of the film is small. is there. As long as the condition that the average particle size is 25 nm or less is satisfied, the silica ultrafine particles 11 may contain some particles exceeding 25 nm to some extent. For example, by using the silica ultrafine particles 11 having a bimodal particle size distribution having a particle size distribution peak between 5 nm and 15 nm and between 30 nm and 120 nm, the unevenness on the surface of the antifouling coating 15 is appropriately increased, Antifouling property can be improved.

  In preparing the aqueous coating composition, when at least one zirconium compound selected from zirconium chloride and zirconyl chloride is added, the silica ultrafine particles 11 have a pH of 4 or less and have a pH of 4 or less in order to make it difficult to form aggregates. It is preferable to use a dispersed dispersion. In order to facilitate the formation of the antifouling coating 15, various kinds of silicates such as sodium silicate and lithium silicate, a general binder such as metal alkylate, aluminum phosphate, and ρ-alumina are used in combination with the silica ultrafine particles 11. May be.

  The content of the ultrafine silica particles 11 may be 0.1% by mass or more and 10% by mass or less, preferably 0.2% by mass or more and 10% by mass or less, more preferably, with respect to the aqueous coating composition. It is 0.2 mass% or more and 4 mass% or less. When the content of the ultrafine silica particles 11 is less than 0.1% by mass, the thickness of the antifouling coating 15 becomes too thin, and sufficient hydrophilicity and dust adhesion suppressing effect cannot be obtained. When the content of the silica ultrafine particles 11 exceeds 10% by mass, the surface of the formed antifouling coating 15 becomes uneven, dust and the like are easily caught, and the antifouling property is inferior.

  The type of the fluororesin particles 12 is not particularly limited. For example, PTFE (polytetrafluoroethylene), FEP (tetrafluoroethylene / hexafluoropropylene copolymer), PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) ), ETFE (ethylene / tetrafluoroethylene copolymer), ECTFE (ethylene / chlorotrifluoroethylene copolymer), PVDF (polyvinylidene fluoride), PCTFE (polychlorotrifluoroethylene), PVF (polyvinyl fluoride), Examples thereof include particles formed from fluoroethylene / vinyl ether copolymers, fluoroethylene / vinyl ester copolymers, copolymers and mixtures thereof, and those obtained by mixing other resins with these fluororesins. The average particle diameter of the fluororesin particles 12 is preferably 50 nm or more and 500 nm or less, more preferably 70 nm or more and 350 nm or less, and most preferably 90 nm or more and 300 nm or less. Here, the “average particle diameter” of the fluororesin particles 12 in the present specification is based on the number of primary particles of the fluororesin particles 12 as measured by a laser light scattering type or dynamic light scattering type particle size distribution meter. Mean value of average particle size. If the average particle size of the fluororesin particles 12 is less than 50 nm, the effect of adding the fluororesin may not be obtained. On the other hand, when the average particle diameter of the fluororesin particles 12 exceeds 500 nm, the surface of the antifouling coating 15 may become too large and the antifouling effect may be impaired.

  When the fluororesin particles 12 are contained in the aqueous coating composition, the content thereof is preferably 70:30 to 95: 5, more preferably 75:25 to 90, as a mass ratio of the silica ultrafine particles 11 and the fluororesin particles 12. : 10. If the ratio of the fluororesin particles 12 is too larger than the above range, the hydrophilicity of the antifouling coating 15 may be too low. Furthermore, many hydrophobic portions resulting from the fluororesin particles 12 may be exposed on the surface, and lipophilic dirt may be easily attached. On the other hand, if the ratio of the fluororesin particles 12 is too smaller than the above range, the hydrophobic portion due to the fluororesin particles 12 is not sufficiently exposed on the surface of the antifouling coating 15, and hydrophilic dirt is likely to adhere, The desired dust adhesion suppression performance may not be obtained. The mass of the silica ultrafine particles 11 and the fluororesin particles 12 herein is a value measured by drying the water-based coating composition at 120 ° C. and removing moisture.

  The thickness of the antifouling coating 15 is not particularly limited, but is preferably 0.05 μm or more and 0.5 μm or less. When the thickness of the antifouling coating 15 is less than 0.05 μm, a desired dust adhesion suppressing effect may not be obtained. On the other hand, when the thickness of the antifouling coating 15 exceeds 0.5 μm, defects such as cracks and voids are likely to occur in the film, and irregularities that easily trap dirt are formed on the surface, and a desired dust adhesion suppressing effect is obtained. There may not be.

  The water-based coating composition preferably contains the fluororesin particles 12 as a resin component, but it is not preferable to mix a resin contained in a coating mainly composed of a general resin component. One of the features of the antifouling coating 15 of the present invention is that it is difficult to adhere dust and the like due to the porous silica film formed by aggregation of the ultrafine silica particles 11. Therefore, if a resin component that fills the gap between the silica ultrafine particles 11 or a resin component that covers the silica ultrafine particles 11 with the entire film is present in the aqueous coating composition, this feature is lost, and the present invention is highly effective. The antifouling effect cannot be obtained. If the particulate resin component does not cover the silica ultrafine particles 11 with the entire film, the problem that the antifouling effect cannot be obtained does not occur.

The content of the resin component that can be added to the aqueous coating composition or the component that reacts to become a resin component is 50% by mass or less of the total amount of the silica ultrafine particles 11, the zirconium compound, and the fluororesin particles 12 (when included). It is preferable that it is 30% by mass or less. The mass of the silica ultrafine particles 11 and the fluororesin particles 12 herein is a value measured by drying the water-based coating composition at 120 ° C. and removing moisture. Further, the content of the zirconium compound is calculated based on the mass of zirconium oxide when all of the zirconium in the added zirconium compound becomes zirconium oxide (ZrO ₂ ). The water-soluble resin component is not included in the content of the resin component described above. Even if the water-soluble resin component is added to the water-based coating composition, the antifouling coating 15 is easily removed by coming into contact with water, and the antifouling property is ensured. Examples of water-soluble resin components include surfactants, dispersants, and flocculants.

  The application method of the aqueous coating composition is not particularly limited, and examples thereof include application by brush coating, spraying, roll coater and the like. In the case of brush coating or spray coating, if excess water-based coating composition remains on the surface and is dried, there is a possibility that inconveniences such as locally forming a thick part and increasing adhesion of dust at that part will occur. Therefore, after applying the solution, it is preferable that the excess aqueous coating composition is discharged by standing or the excess aqueous coating composition is blown off by air blow to eliminate the excess aqueous coating composition. .

  After the antifouling coating 15 is formed, heating is performed as necessary. When heating, it is preferable to leave in an oven at 40 ° C. or higher and 150 ° C. or lower, or by blowing warm air at 40 ° C. or higher and 150 ° C. or lower. At a temperature below 40 ° C., the heating effect does not appear. On the other hand, a temperature exceeding 150 ° C. is not preferable because the hydrophilicity of the antifouling coating 15 is likely to decrease. The heating time is preferably 15 seconds or more and 15 minutes or less. If the heating time is less than 15 seconds, the temperature of the fin material does not increase sufficiently, which is not preferable. When the heating time exceeds 15 minutes, the productivity is poor and the hydrophilicity tends to decrease.

Embodiment 2. FIG.
The antifouling coating according to Embodiment 2 of the present invention has a hydrophilic organic coating as a base for the inorganic coating. By applying the antifouling coating in such a form to the heat exchanger, good characteristics as a heat exchanger can be obtained. Forming a hydrophilic organic coating on the surface of the heat exchanger such as fins as a base, and forming a reaction layer on the hydrophilic organic coating from an aqueous solution containing at least one zirconium compound selected from zirconium chloride and zirconyl chloride; An inorganic coating is formed from an aqueous coating composition containing silica ultrafine particles on the reaction layer, or an inorganic coating from an aqueous coating composition containing silica ultrafine particles and at least one zirconium compound selected from zirconium chloride and zirconyl chloride. By forming, the corrosion of the fin can be suppressed and the hydrophilicity and antifouling property can be maintained over a long period of time. The hydrophilic organic coating has an effect of suppressing corrosion of the heat exchanger surface. Inorganic coating increases the hydrophilicity of the surface, preventing condensation water from forming droplets and increasing ventilation resistance, and suppressing the adhesion of dust and fiber dirt sucked into the heat exchanger Take on.

  FIG. 3 is a schematic diagram for explaining deterioration of a conventional coating due to adhesion of metal particles. In FIG. 3, the conventional coating is formed by laminating an inorganic coating 23 in which ultrafine silica particles 11 are accumulated and dotted with fluororesin particles 12 on a hydrophilic organic coating 22 made of a polymer 21. As described with reference to FIG. 1, the coating having such a configuration hardly adheres to dust, but when it is wet with water, the metal particles 13 (for example, iron powder) adhere to the coating. Metal ions 14 are released from the metal particles 13 when a part of the metal particles 13 is corroded by moisture. The released metal ions 14 pass through the inorganic coating 23 and reach the hydrophilic organic coating 22. The metal ions 14 function as a catalyst and promote the decomposition of the polymer constituting the hydrophilic organic coating 22. As a result, the hydrophilic organic coating 22 is deteriorated, the inorganic coating 23 is peeled off, and a defect as a whole coating occurs. As a result, not only the metal particles 13 are fixed, but also the corrosion proceeds when the base material is a metal. In such a state, the hydrophilicity and dust adhesion suppressing effect of the inorganic coating 23 are reduced.

  On the other hand, the antifouling coating 15 according to Embodiment 2 of the present invention contains at least one zirconium compound selected from zirconium chloride and zirconyl chloride when forming the inorganic coating 23 on the hydrophilic organic coating 22. By using the coating composition, the influence of the metal particles 13 can be suppressed. FIG. 4 is a schematic diagram for explaining that the antifouling coating 15 according to Embodiment 2 of the present invention is hardly deteriorated by the adhesion of the metal particles 13. Zirconium chloride or zirconyl chloride has the effect described in the first embodiment for the inorganic coating 23, but also has the effect of suppressing the influence of the metal particles 13 on the hydrophilic organic coating 22. When an aqueous solution containing at least one zirconium compound selected from zirconium chloride and zirconyl chloride is applied on the hydrophilic organic coating 22, and the silica ultrafine particles and zirconium chloride described in the first embodiment are applied on the hydrophilic organic coating 22. In either case of applying an aqueous coating composition containing at least one zirconium compound selected from zirconyl chloride and water, zirconium chloride or zirconyl chloride acts on the hydrophilic organic coating 22. Zr atoms 16 introduced by zirconium chloride or zirconyl chloride react with a hydroxyl group or the like in the hydrophilic organic coating 22 to crosslink the polymer component and strengthen the hydrophilic organic coating 22. By such a function, the influence of the metal particles 13 can be suppressed. In FIG. 4, the hydrophobic fluororesin particles 12 are scattered on the hydrophilic silica thin film, but the fluororesin particles 12 further suppress the adhesion of dust, and even without this, The effect of suppressing the sticking of the metal particles 13 by adding zirconium chloride or zirconyl chloride can be obtained. That is, the surface of the antifouling coating 15 in such a heat exchanger has a structure in which a hydrophilic part is continuous although a hydrophobic part is present. Has a high hydrophilicity. Also, since the hydrophilic part and the hydrophobic part are finely mixed together, hydrophilic dust such as sand dust and oleophilic dust such as oil smoke come to the surface of the heat exchanger and adhere to it. , It will come into contact with the surface of the opposite properties and cannot adhere stably, and will exhibit a high antifouling property against a wide range of dust contamination.

The hydrophilic organic coating 22 in Embodiment 2 may be a film that contains a polymer having a polar group and does not dissolve in water. The polymer is not particularly limited, but homopolymers of polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, copolymers and modified products thereof, acrylic acid, homopolymers of methacrylic acid, copolymers of these and Examples thereof include salts thereof, various epoxy resins and urethane resins. These may use 1 type and may mix and use a different thing. Moreover, what has a polar group also in a fluororesin and silicone can be used. It may be a mixture of a plurality of types of polymers that are homogeneously mixed or phase-separated, or a mixture of particles and those that function as binders.
In order to insolubilize and improve the strength, the coating composition for forming the hydrophilic organic coating 22 may contain a crosslinking agent, a radical initiator, a reactive component, inorganic particles such as silica and titania, and the like.
The thickness of the hydrophilic organic coating 22 is preferably 0.1 μm or more and 15 μm or less. If the thickness of the hydrophilic organic coating 22 is less than 0.1 μm, it may be too thin to obtain a sufficient anticorrosion effect. On the other hand, if the thickness of the hydrophilic organic coating 22 exceeds 15 μm, the film is too thick, which may reduce the efficiency of heat transfer.

  The reaction of zirconium chloride or zirconyl chloride may be performed on the hydrophilic organic coating 22, the inorganic coating 23, or both.

In order to cause zirconium chloride or zirconyl chloride to directly act on the hydrophilic organic coating 22, an aqueous solution containing zirconium chloride or zirconyl chloride may be applied on the hydrophilic organic coating 22. In this method, the reaction layer is formed by reacting zirconium chloride or zirconyl chloride to the hydrophilic organic coating 22 at a sufficiently high density instead of complicating the process. Such a reaction layer has an advantage that the penetration of the metal ions 14 released from the metal particles 13 into the hydrophilic organic coating 22 can be further suppressed. Further, as described in the first embodiment, the concentration of zirconium chloride or zirconyl chloride in the aqueous coating composition containing the ultrafine silica particles 11, at least one zirconium compound selected from zirconium chloride and zirconyl chloride, and water is the same as that described in the first embodiment. Although it is as low as 50% by mass or less of the solid content weight of the ultrafine particles, the method of applying an aqueous solution containing zirconium chloride or zirconyl chloride can make the concentration higher than that, so that zirconium chloride or zirconyl chloride is a hydrophilic organic It is possible to react the coating 22 with a higher density. Thus, the aqueous solution used when directly reacting with the hydrophilic organic coating 22 preferably contains at least one zirconium compound selected from zirconium chloride and zirconyl chloride in an amount of 0.1% by mass to 40% by mass, More preferably, it is contained in an amount of 0.2% by mass or more and 15% by mass or less. If the zirconium compound is less than 0.1% by mass, the Zr atoms 16 introduced into the hydrophilic organic coating 22 may be too small to obtain a sufficient effect. On the other hand, if the zirconium compound exceeds 40% by mass, excess compound may adhere to the surface and adversely affect the formation of the inorganic coating 23. Here, the content of the zirconium compound is calculated based on the mass of zirconium oxide when all of the zirconium in the added zirconium compound becomes zirconium oxide (ZrO ₂ ).

  The method for applying the aqueous solution is not particularly limited, and examples thereof include application by spraying, roller, dipping, pouring and the like. Drying after application can be performed by natural drying at normal temperature, but by drying with warm air or oven heating, the reaction is promoted and a stronger hydrophilic organic coating 22 can be obtained. The heating temperature at this time is preferably 40 ° C. or higher and 250 ° C. or lower. When the heating temperature is less than 40 ° C., there is only an effect of quick drying. On the other hand, a heating temperature exceeding 250 ° C. is not preferable because the hydrophilic organic coating 22 may be thermally deteriorated to cause cracks. The heat treatment at this time has an advantage that it can be applied even at a temperature that causes problems such as a decrease in hydrophilicity when applied to the inorganic coating 23.

  Next, an antifouling coating 15 comprising the hydrophilic organic coating 22, the reaction layer and the inorganic coating 23 is formed by applying an aqueous coating composition containing the silica ultrafine particles 11 on the reaction layer to form the inorganic coating 23. can get. The kind and content of the silica ultrafine particles 11 used here are the same as those in the first embodiment. Moreover, the water-based coating composition used here may contain the fluororesin particles 12, and the kind and content thereof are the same as those in the first embodiment.

  The application method of the aqueous coating composition is not particularly limited, and examples thereof include application by brush coating, spraying, roll coater and the like. In the case of brush coating or spray coating, if excess water-based coating composition remains on the surface and is dried, there is a possibility that inconveniences such as locally forming a thick part and increasing adhesion of dust at that part will occur. Therefore, after applying the solution, it is preferable that the excess aqueous coating composition is discharged by standing or the excess aqueous coating composition is blown off by air blow to eliminate the excess aqueous coating composition. .

  After forming the inorganic coating 23, it heats as needed. When heating, it is preferable to leave in an oven at 40 ° C. or higher and 150 ° C. or lower, or by blowing warm air at 40 ° C. or higher and 150 ° C. or lower. At a temperature below 40 ° C., the heating effect does not appear. On the other hand, a temperature exceeding 150 ° C. is not preferable because the hydrophilicity of the inorganic coating 23 is likely to deteriorate. The heating time is preferably 15 seconds or more and 15 minutes or less. If the heating time is less than 15 seconds, the temperature of the fin material does not increase sufficiently, which is not preferable. When the heating time exceeds 15 minutes, the productivity is poor and the hydrophilicity tends to decrease.

  On the other hand, in order to allow zirconium chloride or zirconyl chloride to act on both the hydrophilic organic coating 22 and the inorganic coating 23, the hydrophilic organic coating 22 and the inorganic coating 23 are formed and then selected from zirconium chloride and zirconyl chloride. There is a method of treating with an aqueous solution containing at least one zirconium compound. As an advantageous method in terms of process simplification over this method, at least one zirconium compound selected from the silica ultrafine particles 11 described in Embodiment 1, zirconium chloride and zirconyl chloride on the hydrophilic organic coating 22 is used. There is a method of applying an aqueous coating composition containing water and water. In this method, a step of applying an aqueous solution containing at least one zirconium compound selected from zirconium chloride and zirconyl chloride can be omitted, and adhesion between the hydrophilic organic coating 22 and the inorganic coating 23 can be increased. .

  As a method for ensuring the reaction of zirconium chloride or zirconyl chloride, a method of increasing the contact time between the aqueous coating composition and the hydrophilic organic coating 22 before drying, for example, increasing the immersion time in the aqueous coating composition Or the spraying time of the water-based coating composition is increased. The reaction can be sufficiently advanced by setting the contact time to 10 seconds or longer, preferably about 30 seconds, by this method. If the contact time is less than 10 seconds, there is no difference from normal application. Even if the contact time exceeds 30 seconds, there is almost no change in the effect, which is not preferable. As another method for further ensuring the reaction of zirconium chloride or zirconyl chloride, there is a method of raising the temperature of the aqueous coating composition or the object to be coated. By making this temperature 30 ° C. or more and 60 ° C. or less, the reaction can be easily advanced. At temperatures below 30 ° C., the heating effect is too small. When the temperature exceeds 60 ° C., the water-based coating composition evaporates vigorously, and the drying becomes faster. On the contrary, the reaction to the hydrophilic organic coating 22 is difficult to proceed, and uniform application becomes difficult.

  When the antifouling coating 15 described above is formed on the fins of the heat exchanger, it is preferable to join the pipe through which the refrigerant passes and the fins, assemble the heat exchanger, and then apply the coating composition onto the fins. If the heat exchanger is assembled after the antifouling coating 15 is formed on the fins, the antifouling coating 15 may be damaged due to steps such as punching of the fin material, pressing, and tube insertion. is there. This can be avoided by joining the pipe through which the refrigerant passes and the fin, assembling the heat exchanger, and then applying the coating composition on the fin. The application method at this time can be spraying or dipping. After applying the coating composition or aqueous solution, the excess liquid is removed by a method of discharging the excess liquid by standing, a method of shaking off the excess liquid by a motion such as rotation of a heat exchanger, or a method of blowing off the excess liquid by air blow. It is preferable. Moreover, it is also preferable to apply the aqueous solution or the aqueous coating composition after forming the hydrophilic organic coating 22 only on the fin material before assembly and assembling the heat exchanger.

EXAMPLES Hereinafter, although an Example demonstrates the detail of this invention, this invention is not limited by these.
[Example 1]
Pure water, colloidal silica (Snowtex OXS manufactured by Nissan Chemical Industries, Ltd.) containing silica ultrafine particles having an average particle diameter of 6 nm, PTFE dispersion having an average particle diameter of 150 nm, and zirconium chloride (12% by mass of the silica ultrafine particles) Are mixed with stirring, 0.1% by mass of a nonionic surfactant (polyoxyethylene lauryl alkyl ester) is added to the mixture, and the mixture is further stirred and mixed to obtain an aqueous coating composition having the composition shown in Table 1. A product was prepared.
The obtained aqueous coating composition was applied to an aluminum fin material and dried by air blow. The aluminum fin material after the coating was formed was dipped in water and wetted, and iron powder with an average particle diameter of 45 μm was sprayed. After drying by air blow, the adhesion state of the iron powder was observed. The adhesion state of the iron powder was visually determined. When iron powder adheres to an untreated aluminum fin material (Comparative Example 4), a large amount of iron powder adheres, so this is set to 5 and no iron powder adheres at all. Was determined in 6 stages.
The aluminum fin material to which the iron powder was adhered was allowed to stand for 3 days at a humidity of 90%, and then sprayed with a water stream to visually check the contamination status.
The contact angle was measured using a contact angle meter PD-X (Kyowa Interface Science).
The results are shown in Table 2.

[Example 2]
Pure water, colloidal silica (Snowtex OXS manufactured by Nissan Chemical Industries, Ltd.) containing silica ultrafine particles having an average particle diameter of 6 nm, PTFE dispersion having an average particle diameter of 150 nm, and zirconium chloride (10% by mass of the silica ultrafine particles) Are mixed with stirring, 0.1% by mass of a nonionic surfactant (polyoxyethylene lauryl alkyl ester) is added to the mixture, and the mixture is further stirred and mixed to obtain an aqueous coating composition having the composition shown in Table 1. A product was prepared. An aluminum fin material on which a coating was formed was produced in the same manner as in Example 1 except that this aqueous coating composition was used. This was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Example 3]
An aluminum fin material on which a coating was formed was produced in the same manner as in Example 1 except that zirconyl chloride was used instead of zirconium chloride. This was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Example 4]
An aluminum fin material on which a coating was formed was produced in the same manner as in Example 2 except that zirconyl chloride was used instead of zirconium chloride. This was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Example 5]
An aluminum fin material on which a coating was formed was produced in the same manner as in Example 1 except that the PTFE dispersion was not used. This was evaluated in the same manner as in Example 1.
The results are shown in Table 2.

[Comparative Example 1]
An aluminum fin material on which a coating was formed was produced in the same manner as in Example 1 except that the content of zirconium chloride was changed to 60% by mass of the ultrafine silica particles. This was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Comparative Example 2]
An aluminum fin material on which a coating was formed was produced in the same manner as in Example 1 except that zirconium chloride was not used. This was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Comparative Example 3]
An aluminum fin material on which a coating was formed was produced in the same manner as in Example 1 except that PTFE dispersion and zirconium chloride were not used. This was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Comparative Example 4]
An untreated aluminum fin material (aluminum fin material on which no coating was formed) was evaluated in the same manner as in Example 1. The results are shown in Table 2.

  From the results shown in Table 2, the adhesion of the iron powder is less than that of the untreated aluminum fin material of Comparative Example 4 in which the silica fine particle film was applied (Comparative Example 3). The number to which the fluororesin particles are applied (Comparative Example 2) is further reduced. What mixed excess zirconium chloride (comparative example 1) has the small inhibitory effect of iron powder adhesion. As for hydrophilicity, all are improved by coating, but it is understood that the mixture of excess zirconium chloride (Comparative Example 1) is lowered.

In each of Examples 1 to 5, high hydrophilicity is obtained, and adhesion of iron powder is small. In Example 5, iron powder adheres a little more than in Examples 1 to 4, but this is because no fluororesin particles are added. Moreover, compared with the comparative example 3, Example 5 has less adhesion of iron powder. This indicates that the addition of zirconium chloride suppresses the adhesion of iron powder.
When the iron powder is corroded, in Comparative Examples 2 to 4 in which no zirconium compound is added, the rust is firmly fixed on the surface and is not peeled off by the spray, whereas in Examples 1 to 5 and Comparative Example 1, the rust is Sticking is greatly suppressed. Furthermore, in Examples 1-5, while showing high hydrophilicity and a dust adhesion inhibitory effect, it turns out that it is hard to adhere even when the adhered iron powder corrodes.

[Examples 6 and 7]
An aqueous solution prepared by mixing 3% by weight of polyvinyl alcohol Z-200 (Nippon Synthetic Chemical) and 5% by weight of glyoxal with respect to polyvinyl alcohol was applied to an aluminum fin material, heated at 150 ° C. for 5 minutes, and a thickness of 0.7 μm. A hydrophilic organic coating was formed. A 5% by mass aqueous solution of zirconyl chloride was applied on the hydrophilic organic coating and dried by air blowing at room temperature to form a reaction layer (pretreatment). Thereafter, an aqueous coating composition having the composition shown in Table 3 was applied onto the reaction layer and dried by air blowing to form an inorganic coating.
The aluminum fin material after the coating was formed was dipped in water and wetted, and iron powder with an average particle diameter of 45 μm was sprayed. After drying by air blow, the adhesion state of the iron powder was observed. The adhesion state of the iron powder was visually determined. In the case of only the hydrophilic organic coating (Comparative Example 5), since it was in a state of being completely blackened, this was set to 5, and the state in which no iron powder was adhered was set to 0, and the determination was made in 6 stages.
Further, after being left for 3 days at a humidity of 90% with the iron powder adhered, a water flow was blown with a spray to confirm the state of the corroded iron powder. Moreover, it immersed in 1% sodium hydroxide aqueous solution for 1 minute, and the change of the coating of iron powder vicinity was confirmed. The results are shown in Table 4.

[Examples 8 and 9]
An aqueous solution prepared by mixing 3% by weight of polyvinyl alcohol Z-200 (Nippon Synthetic Chemical) and 5% by weight of glyoxal with respect to polyvinyl alcohol was applied to an aluminum fin material, heated at 150 ° C. for 5 minutes, and a thickness of 0.7 μm. A hydrophilic organic coating was formed. On the hydrophilic organic coating, an aqueous coating composition having the composition shown in Table 3 was applied on the reaction layer, dried by air blowing to form an inorganic coating, and an aluminum fin material on which the coating was formed was produced. This was evaluated in the same manner as in Examples 6 and 7. The results are shown in Table 4.

[Comparative Example 5]
An aqueous solution prepared by mixing 3% by weight of polyvinyl alcohol Z-200 (Nippon Synthetic Chemical) and 5% by weight of glyoxal with respect to polyvinyl alcohol was applied to an aluminum fin material, heated at 150 ° C. for 5 minutes, and a thickness of 0.7 μm. A hydrophilic organic coating was formed to produce an aluminum fin material on which the coating was formed. This was evaluated in the same manner as in Examples 6 and 7. The results are shown in Table 4.

[Comparative Examples 6 and 7]
An aqueous solution prepared by mixing 3% by weight of polyvinyl alcohol Z-200 (Nippon Synthetic Chemical) and 5% by weight of glyoxal with respect to polyvinyl alcohol was applied to an aluminum fin material, heated at 150 ° C. for 5 minutes, and a thickness of 0.7 μm. A hydrophilic organic coating was formed. On the hydrophilic organic coating, an aqueous coating composition having the composition shown in Table 3 was applied on the reaction layer, dried by air blowing to form an inorganic coating, and an aluminum fin material on which the coating was formed was produced. This was evaluated in the same manner as in Examples 6 and 7. The results are shown in Table 4.

  It is hydrophilic from the contact angle, antifouling performance from the state after wet adhesion and drying of iron powder, and from the state of iron powder fixation after washing with water, the iron rust adhesion state, the coloration state by iron ions, the iron after alkali cleaning The degree of deterioration of the hydrophilic organic coating due to iron ions can be seen from the coating state of the powder adhering portion.

  From the results in Table 4, Comparative Example 5 has a low hydrophilicity with a contact angle of 45 ° in a dry state. In Comparative Example 5, the hydrophilicity is increased in a humidified state, and the water becomes familiar with water. In Comparative Example 5, iron powder tends to adhere and the antifouling property is low. In Comparative Example 5, when stored in a humidified state, iron rust was fixed, and the coating was also changed to brown black. This indicates that dust containing iron powder or the like is likely to stick. Further, in the alkali cleaning, the coating was dissolved and peeled off at the iron powder adhering portion. From this, it can be seen that the film is deteriorated by the generated iron ions.

  In Comparative Examples 6 and 7, the hydrophilic organic coating is covered with an inorganic coating. From the contact angle, it can be seen that the hydrophilicity is high and the antifouling property is also high from the state of iron powder adhesion. However, it can be seen that the iron rust is easily fixed by storage in a humidified state, and the hydrophilic organic coating is deteriorated and peeled off.

  Examples 6 and 7 have high hydrophilicity and high antifouling performance. It can be seen that the influence of iron ions is suppressed because there is little fixation and coloring even with iron powder corrosion, and there is no peeling of the hydrophilic organic coating due to alkali. In particular, coloring of the hydrophilic organic coating is greatly suppressed, and it is considered that the polymer component is efficiently protected by directly treating the hydrophilic organic coating. In comparison between Example 6 and Example 7, the antifouling performance of Example 7 is superior, and the effect of adding fluororesin particles appears.

  Examples 8 and 9 have high hydrophilicity and high antifouling performance. It can be seen that the influence of iron ions is suppressed because there is little fixation and coloring even with iron powder corrosion, and there is no peeling of the hydrophilic organic coating due to alkali. In particular, iron rust sticking is greatly suppressed, and it is considered that the inorganic coating is efficiently protected by the addition of zirconium chloride to the inorganic coating. In the comparison between Example 8 and Example 9, the antifouling performance is better in Example 9, and the effect of adding fluororesin particles appears.

  11 Ultrafine silica particles, 12 Fluorine resin particles, 13 Metal particles, 14 Metal ions, 15 Antifouling coating, 16 Zr atom, 21 Polymer, 22 Hydrophilic organic coating, 23 Inorganic coating.

Claims (5)

After joining the fin formed with the hydrophilic organic coating to the pipe through which the refrigerant passes, a reaction layer is formed on the hydrophilic organic coating from an aqueous solution containing at least one zirconium compound selected from zirconium chloride and zirconyl chloride. An inorganic coating is formed from an aqueous coating composition containing 0.1 to 10% by weight of silica ultrafine particles having an average particle size of 25 nm or less on the reaction layer, or 25 nm or less on the hydrophilic organic coating. 0.1 to 10% by mass of silica ultrafine particles having an average particle diameter, 5 to 50% by mass of silica ultrafine particles selected from at least one zirconium compound selected from zirconium chloride and zirconyl chloride, and 30 to 99 water. Forming an inorganic coating from an aqueous coating composition containing 5% by weight Method of manufacturing a heat exchanger, characterized in that it comprises. The aqueous coating composition, method for producing a heat exchanger according to claim 1, wherein the fluororesin particles further including that a having an average particle size of 50 to 500 nm.   A heat exchanger comprising a pipe through which a refrigerant passes and a fin attached to the pipe, the hydrophilic organic coating formed on the fin, and zirconium chloride and zirconyl chloride on the surface of the hydrophilic organic coating An inorganic layer formed from a reaction layer obtained by reacting at least one selected zirconium compound and an aqueous coating composition containing 0.1 to 10% by mass of silica ultrafine particles having an average particle diameter of 25 nm or less on the reaction layer. And a heat exchanger. A pipe through which the refrigerant, a heat exchanger and a fin attached to the pipe, and a hydrophilic organic coating formed on the fin, on the hydrophilic organic coating, 2 5 nm or less in average particle 0.1 to 10% by mass of silica ultrafine particles having a diameter, 5 to 50% by mass of silica ultrafine particles selected from at least one zirconium compound selected from zirconium chloride and zirconyl chloride, and 30 to 99.5 water. A heat exchanger comprising an inorganic coating formed from a water-based coating composition containing mass%. Containing 0.1 to 10% by mass of silica ultrafine particles having an average particle size of 25 nm or less,
Containing at least one zirconium compound selected from zirconium chloride and zirconyl chloride in an amount of 5 to 50% by mass of the silica ultrafine particles,
Fluorine resin particles having an average particle diameter of 50 to 500 nm are included in an amount of 70:30 to 95: 5 in a mass ratio of the silica ultrafine particles to the fluorine resin particles,
The antifouling coating is formed from an aqueous coating composition containing 30 to 99.5% by mass of water.

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